Secretion of growth hormone (GH) is pulsatile. The mechanism by which GH pulses are caused is unkown. Possible explanations include pulsatile secretion of growth hormone-releasing hormone (GHRH), periodic declines of somatostatin (SRIH), a combination of both, or involvement of other central neuroendocrine regulatory molecules/factors. Our previous studies demonstrated that GHRH is required for pulsatile GH release. However it is possible that GHRH is simply permissive and that SRIH withdrawal is primarily responsible for GH pulses. In addition, and endogenous ligand to the recently cloned growth hormone releasing peptide (GHRP) might be important in the generation of GH pulses. In this study we will investigate the secretory pattern of GH in postmenopausal women and the possible role of the above mentioned factors.